The Curious Case of Database Deduplication. PRESENTATION TITLE GOES HERE Gurmeet Goindi Oracle

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1 The Curious Case of Database Deduplication PRESENTATION TITLE GOES HERE Gurmeet Goindi Oracle

2 Agenda Introduction Deduplication Databases and Deduplication All Flash Arrays and Deduplication 2

3 Quick Show of Hands How many Storage administrators? How many System administrators? How many Network administrators? How many Database administrators? Neither? Example, Managers? 3

4 Enterprise Data Growth Enterprise data is growing 10-20% per year Some industries upwards of 50%+ data growth / annually Increase in production data is magnified in the backup storage infrastructure More production data expands exponentially into the backup storage infrastructure Year over year data growth! 4

5 Exponential Growth in Backup Infrastructure Data Growth Multiples in Backup Copies: Production Data Size Last Year: This Year: One Month of Backups Backup retention periods remain constant based on business needs Often expanding due to regulatory requirements Storage budget doesn t scale with data growth Data center space and power constraints hamper storage scale-outs 5

6 Backup Storage Optimization Strategies Backup Compression Software (e.g. native utilities) Hardware (e.g. tape or disk drives) Deduplication Source Side (software) Purpose Built Backup Appliances Hybrid Approach 6

7 Agenda Introduction Deduplication Concepts Databases and Deduplication All Flash Arrays and Deduplication 7

8 Deduplication 101 Deduplication: Replace redundant backup data with pointers to shared copy Redundant data identified by unique algorithms Lowers storage costs by reducing capacity requirements Can be done at source, inline or post-process Mileage varies for deduplication of database blocks 8

9 Deduplication Internals Is the Fingerprint Unique? Yes Write to storage, update the metadata Backup Data Deduplication Engine Hash / Fingerprint No Update the metadata Matches Duplicate Found: Bit Compare with existing block Doesn t Match Write to storage, update the metadata 9

10 Deduplication & Compression Compression is about shrinking the dataset Encoding information using fewer bits than the original representation Examples: Lempel-Ziv (LZ) compression Deduplication is about finding unique datasets and reducing redundant dataset Deduplicated dataset can be further compressed Compressed dataset will yield poor and unpredictable deduplication ratios 10

11 Source Side Deduplication Deduplication software is installed on each host Software reads the data to be backed up and looks for duplicates Transmits the deduped backup to a storage appliance, for most cases Performance impact: Host : High Network: Low Usually the backups need to be reconstituted when copied to tape 11

12 Target Side Deduplication Deduplication occurs at backup/storage appliance Two flavors: Inline Backup is deduplicated prior to being written to disk Post-process Backup is written to a staging area, then deduplicated Performance Impact: Host : High Network: High Backups must be reconstituted when copied to tape 12

13 Agenda Introduction Deduplication Concepts Databases and Deduplication All Flash Arrays and Deduplication 13

14 Databases And Deduplication Leading vendor 30x times deduplication for File Systems 6x for Relational Databases Emerging all Flash array vendor 10x saving for file systems 2.1x for Relational Databases Most vendors recommend full backups to achieve better deduplication ratios What drives low deduplication ratios for databases? 14

15 Relational Databases Quick Intro Relational database: repository and management of data organized in a relational model * Database Management System (DBMS): the software infrastructure to maintain these key characteristics: Structures: Well-defined objects to store data Operations: Well-defined actions to access & update data & structure Integrity rules: Well-defined rules to govern operations Data organized in a table: a two-dimensional relation with rows (tuples) and columns (attributes) Each row in a table has the same set of columns E.g. employee, department, salary tables 15

16 Databases and Storage Database Objects Reads and Writes Meta data associated with these Objects Database Logging Mechanism to deliver transactional consistency Critical functionality for database operation Availability features 16

17 Database Block Format Database manages its logical storage in data blocks Minimum unit of I/O A data block has a welldefined structure Block header is kept consistent with payload, rows do not overlap, metadata in its place More than simple bits: can always verify logical consistency 17

18 Database Block Format.. Contd Even the row (user) data is very carefully formatted within a database data block Blocks have a fixed size (usually 8K) All blocks are unique Update to a block will result in metadata updates to adjacent blocks as well 18

19 Understanding Database Backup Options Image copy: Full Backups Fairly efficient for restore Inefficient use of Server, Network and Storage resources Might Provide Better deduplication ratios Application aware intelligent image copy Better storage and network resource utilization, but not for server workload Faster restore times compared to incremental copies Incremental Backups Transmit only changes on a periodic basis Efficient use to storage, network and server resources Time to recover depends on the number of incremental backups needed to be restored Faster than any full backup strategy, reduces backup window Most successful Database backup strategies include a combination of the two approaches to meet your Recovery Objectives 19

20 Incremental Backups And Deduplication Changed data B 9 A C B A C 8 Full Backup Sunday Incremental Monday Incremental Tuesday Incremental Wednesday Full Backup Thursday Blocks Transmitted All A B C All A database aware incremental backup only has unique blocks Deduplication ratios are minimal / unpredictable Limited to duplicates in the user data within the block Low impact on database server and network 20

21 Full Backups And Deduplication Changed data B 9 A C B A C 8 Full Backup Sunday Full Backup Monday Full Backup Tuesday Full Backup Wednesday Full Backup Thursday Blocks Transmitted All All All All All Huge number of redundant blocks transmitted In the above example: almost 80% of the traffic is redundant With a typical 5%-10% churn rate nearly 90-95% traffic will be redundant Hence deduplication ratios are high Significant impact on database server and network 21

22 Database Compression and Deduplication Several database integrated compression techniques: OLTP data compression on user data Columnar compression Backup compression Most will yield unpredictable deduplication performances on the backup stream Similar implications with encryption as well 22

23 What About Database Logs? Fundamental structure of the database: transaction logs Most crucial structure for data recovery Contents: change data, undo data, schema / object management statements, etc. Well-defined data fields, relationships Almost zero scope for deduplication REDO RECORD - Thread:1 RBA: 0x00003e.0000d188.01b0 LEN: 0x07c8 VLD: 0x01 SCN: 0x d6ca18 SUBSCN: 1 04/30/ :06:42 CHANGE #1 TYP:0 CLS:67 AFN:3 DBA:0x00c1fbb1 OBJ: SCN:0x d6ca15 SEQ: 1 OP:5.2 ktudh redo: slt: 0x0007 sqn: 0x flg: 0x000a siz: 120 fbi: 0 uba: 0x00c pxid: 0x

24 To Summarize Is deduplication not the correct design choice for Database backups? Well, it depends Better deduplication ratios possible: With daily full backups May not be practical, based on database size By disabling database compression / encryption Consistent with your security / capacity policies? After customizing backup parameters Need to balance database / dedupe best practices For storage efficiency, do the testing + math Daily incremental backups + native compression VS. Daily full backups + 3rd party dedupe 24

25 Agenda Introduction Deduplication Concepts Databases and Deduplication All Flash Arrays and Deduplication 25

26 Deduplication And All Flash Arrays Solid State Drives are still 5-10x more expensive than Hard Disk Drives Economics of SSDs improve as the footprint of the dataset to be stored is reduced Some All Flash Array vendors are leveraging deduplication to increase the storage efficiency of SSDs Deduplication ratios are fairly modest compared to that seen in secondary storage or Purpose Built Backup Appliances 26

27 Deduplication in All Flash Arrays Technology Enablers Is the Fingerprint Unique? Yes Write to storage, update the metadata Dataset Deduplication Engine Hash / Fingerprint No SSDs accelerate read I/O by many folds thus accelerating bit comparisons and fingerprint lookups Duplicate Found: Bit Compare with existing block Matches Update the metadata Fewer writes result in higher flash endurance Less strong hashing allows the array to leverage in-built CPU hashing functions to generate the fingerprint Doesn t Match Write to storage, update the metadata 27

28 Databases, Deduplication and All Flash Arrays Most All Flash Arrays use fixed length chunk size By definition each database block update results in a unique block and changes to metadata of adjacent blocks Algorithms that are unaware of database block boundary will generate a unique hash for each update Thus defeating the purpose of deduplication 28

29 Questions? 29